Observations on Pancreatic Rennet. 



5 



pro-rennet), and that under the influence of very small quantities 

 of acid at the optimum temperature, the pro-rennet is rapidly 

 transformed into the active rennet. This result is regarded as 

 the product of true activation. Hedin 5 , however, interprets the 

 facts in another manner. He assumes that the pro-rennet is 

 merely a combination of rennet with a substance antagonistic 

 to it, and on the following grounds. If the pro-rennet be treated 

 with dilute HC1, the rennet is set free and the antagonistic sub- 

 stance destroyed, hence, its inhibitory action is lost. On the 

 contrary, a solution of pro-rennet, treated with very dilute am- 

 monia at 37 0 C, loses all its rennet already free, while the an- 

 tagonistic substance remains unchanged ; so that, by adding active 

 rennet to this treated liquor, the rennet is at once rendered in- 

 active. 



I applied Hedin's method of proof to the rennet in the pan- 

 creatic extract and found that the results were in accord with his. 

 On closer analysis it became evident that Hedin's proof was in- 

 sufficient and the conclusion erroneous. 



Before proceeding to the evidence in substantiation of this, 

 permit me to note the following concerning the pancreatic rennet. 

 The content of this enzyme in pancreatic extract is very large, and 

 goes absolutely hand in hand with the quantity of trypsin present. 

 Means have not yet been found to separate rennet from trypsin. 

 The two appear to be intimately associated functionally and 

 chemically. A method has been devised for the quantitative 

 recovery of the rennet-trypsin enzyme and for its purification. 

 This will be presented at another time. Suffice it to say for the 

 present that the trypsin-rennet combination constitutes about 

 1-2 per cent, of the total substance of dried pancreatic extract. 

 It is of protein nature, is not precipitated by colloidal iron, is 

 coagulated by heat (at 82-85 0 C), is extremely hygroscopic, and 

 of an acid character. 



It is active only in the presence of Ca, which, however, must be 

 available in ionizable form. In this fact seems to lie the fault in 

 Hedin's proof. 



I have stated that fresh or well-preserved pancreatic extract 

 has no milk coagulating properties, but when a solution of it is 



6 Hedin, S. G., Harvey Lectures, 1914, p. 162. 



